Centrifugal casting method



July 22, 1969 A. E. SCHUH CENTRIFUGAL CASTING METHOD 3 Sheets-Sheet 1Filed Feb. 7, 1966 FIGJ FIGZ

I N VENT OR ATTORNEY Ari/H1! Sc/mh BY Ed 9. W

y 2, 1969 A. E. SCHUH 3,456,712

CENTRIFUGAL CASTING METHOD Filed Feb. 7, 1966 3 Sheets-Sheet 2 INVENTORArthur E. Sc/w/u BY p W ATTORNEY y 22, 1969 v A. E. SCHUH 3,456,712

CENTRIFUGAIJ CASTING METHOD Filed Feb. 7, 1966 3 Shets-Sheet 5 FIG?Arthur E. Sc/vuh ATTORNEY IN VENTOR 3,456,712 CENTRIFUGAL CASTING METHODArthur E. Schuh, Riverton, N.J., assignor to United States Pipe andFoundry Company, Birmingham, Ala., a corporation of New Jersey FiledFeb. 7, 1966, Ser. No. 525,435 Int. Cl. B22d 13/02, 13/10; B22c 3/00 US.Cl. 164-72 4 Claims ABSTRACT OF THE DISCLOSURE The present inventionrelates to the manufacture of tubular metal castings, and moreparticularly is concerned with the manufacture of cast iron pipe havingbell and spigot ends in permanent metal molds rotated substantiallyhorizontally.

It is well known to cast pipe in permanent metal molds, such methodshaving been practiced extensively in this country for many years.Present methods comprise the use of cylindrical metal molds mounted onrollers in a water jacket and adapted to be rotated at suitable speeds.The water jacket is mounted on a carriage that can be moved by means ofa hydraulic cylinder in the direction of the longitudinal axis of themold on a fixed bed inclined slightly from the horizontal. The molteniron is fed into the mold through a trough similarly inclined. Incasting, a ladle containing molten iron is tilted at a uniform rate tomaintain a constant pouring rate. When the mold is at the extreme upperend of the fixed bed, it is ready for casting at which time the troughextends down the barrel of the mold for nearly its full length. Afterthe casting ladle has been filled by the transfer ladle, the machineoperator brings the bold up to speed and actuates the mechanismcontrolling the tilting of the ladle. In a few seconds the iron hasfilled the bell space at which time the operator starts moving the moldcarriage longitudinally down the bed. The stream of iron discharged fromthe trough fiows onto the surface of the mold, where it is held in placeby centrifugal force and forms the pipe.

Early in the development of such machines it was discovered that farbetter results are obtained if, instead of pouring the iron onto thebare mold, a dry unbonded powdery material such as ferro-silicon isapplied on the inner mold surface just ahead of the iron steam. Whileconstituting a definite improvement, the use of such linings neverthlessdoes not result in completely acceptable pipe, there always beingso-called pinholes or laps or cold shuts.

Perhaps the greatest stride in overcoming these disadvantages of castingpipe in permanent metal molds was the invention described in Schuh eta1. Patent No. 2,399,606 and known in the art as wet spray. Brieflystated, that invention comprises spraying the inner surface of the metalmold with a liquid suspension of a powdered refractory material and abinder to form'incrementally an insulating coating adherent to the moldand having a multiplicity of spaced protuberances von its inner face.

One of the distinct advantages of using permanent metal molds is thespeed with which a great number of pipes can be cast, as compared toother methods such as pit casting and centrifugal casting in sand linedmolds. Maxinited States Patent mum casting speeds have not beenattained, however, due to the necessity of moving the mold through twotwoway strokes for each pipe cast. One two-way stroke is required forpouring the metal throughout the length of the mold, while moving themold relative to the pouring trough, and extracting the cast pipe byreturn of the mold to casting position. An additional two-way stroke isrequired to apply the wet spray mold coating and to posirtion the moldin a convenient position for setting the bell core. It has notpreviously been considered possible to use wet spray coatings except ina four stroke cycle when using the retractive pour method.

It is, accordingly, the principal object of the present invention toprovide a casting procedure or method for producing pipe by theretrac-tive pour method wherein only one two-way stroke of the mold isrequired for the production of each pipe and a wet spray coating isused.

Another object of the invention is the provision of a casting methodwhereby pipe can be made in a permanent metal mold without the necessityof a separate two-way traverse of the mold for insertion of a bell coreor for applying a mold coating.

Still a further object is to provide a method for casting metal pipe ina permanent mold in which the mold is moved in one direction along itshorizontal axis to form the pipe and is moved in the opposite directionto extract the pipe and put the mold in position for another cycle.

Still another object is the provision of a method for casting metal pipein a permanent metal mold in a shorter time than heretofore consideredpossible.

This invention has other objects that will be apparent from aconsideration of the method described herein and of the specificembodiment shown in the drawings accompanying and forming part of thepresent specification. Such form will now be described in detail toillustrate the general principles of the invention, but it is to beunderstood that such detailed description is not to be taken in alimiting sense, since the scope of the invention is defined bythe-claims appended hereto. In the drawings:

FIGURE 1 is a top view in cross section of a pipe casting machinesuitable for practicing the process of illustrating the position of themachine components at the start of a casting cycle.

FIGURE 2 illustrates the position of the machine components at anintermediate stage in the casting cycle.

FIGURE 3 illustrates the position of the machine components at the endof a casting cycle.

FIGURES 4-7 illustrate suitable positions for the spraying nozzle withrespect to the spout end of the pouring trough.

The present process can be carried outwith any retractive pour castingmachine and, accordingly, only a brief. description of a representativecasting machine is given. Turning to FIGURES 1-3, such a machinecomprises a Water box 1 which is mounted on wheels 2 riding on tracks 3.Rotatably mounted on rollers 4 within the water box is mold 5 which isdriven by motor 6 through poly-Y in the mold and secures it in placewhile the pipe is belt 7. At one end of the carriage a puring. trough 8is,

mounted with its longitudinal axis substantially coaxial with the axisof the mold so that its pouring spout 9 traverses the length of the mold4 when water box 1 is moved by means of hydraulic. cylinder 10. Adjacentthe fixed end of trough 8 there is tiltably mounted a machine ladle 11which can be tilted at a uniform rate by con-v ventional drive means,not shown. 7

In order to permit the attainment of the full benefit of the process ofthe present invention, the casting machine is preferably provided with acore setting mechanism which holds a core in position outside the molduntil the proper time in the casting cycle when it quickly seats thecore being cast. This core setting apparatus comprises an arm 12 whichis secured to a shaft 13 and on its free end it is provided with abearing support 14 in which a boss is rotatably mounted. Core 15 isseated on the boss and is backed up by flange 16 secured to the boss.Shaft 13 extends through a sleeve 17 and is secured to the rod of afluid cylinder 18 by means of coupler 19. Sleeve 17 is provided with aslot 20 into which pin 21 projecting from shaft 13 extends. Slot 20 asillustrated consists of a helical portion with a longitudinal portion ateach end. In FIGURE 1, pin 21 is positioned in the slot 20 so that core15 is seated in the end of the mold. When the rod of the fluid cylinderis extended as shown in FIGURE 2, pin 21 is moved from one longitudinalportion of the slot, through the helical portion of the slot, and intothe opposite longitudinal portion of the slot. In so doing shaft 13 ismoved longitudinally and rotated so that the free end of arm 12 is movedaway from and clear of the end of the mold. A new core 15 is placed onthe core setter and held in position until the movement of the fluidcylinder 18 is reversed and it is thereby moved into alignment with andseated in the end of the mold.

In order to carry out the present process, it is necessary to provide aspray nozzle 23 near the end of the pouring trough. This nozzle is fedby means of fluid lines 24 which are secured to the side of trough 8iand covered with shield 25. In addition, since the spray nozzle 23 mustbe positioned away from the pouring spout 9 of the trough, it cannotprovide an adequate coating in the bell cavity of the mold, therefore,spray nozzle 26 is mounted on the end of swinging arm 27. This armswings into the position shown in FIGURE 3 at the end of a casting cycleto spray the bell caviy before core 15 is seated in the mold at thestart of a new casting cycle.

The series of steps comprising the casting process of the presentinvention will now be described with particular reference to FIGURES 1-3which depict diagrammatically the operations performed and the positionsof the components of the apparatus at different stages of the castingcycle. In the first position, FIGURE 1, the mold surrounds the pouringtrough. As was explained above, the bell end of the mold was coated atthe end of the extraction stroke in the previous casting cycle, and thecore was seated in the end of the mold by moving shaft 13 towardcylinder 18. As the shaft rotates due to pin 21 moving through thehelical part of slot 20 the core 15 is moved into alignment with the endof the mold 5, and as the pin then moves along the longitudinal portionof the slot the core is seated in the mold.

Ladle 11 is tilted at a uniform rate causing a stream of metal to flowdown trough 8 into the spinning mold. Preferably, ladle dump is actuallystarted before the core is set in place so that there will be verylittle delay between the time the core is set in the mold and metalfirst starts to pour into the mold. When metal fills up the bell cavity,cylinder is activated to withdraw the mold 5 from trough 8, and :a fanspray of coating is applied to the mold simultaneously through nozzle23. As a result, coating material and molten metal are applied along thelength of the mold, the leading edge of the spray being only a shortdistance ahead of the leading edge of the molten metal at all times,e.g. three or four inches.

When the mold is completely withdrawn from trough 8 and positioned withits bell end adjacent bumping block 28 as shown in FIGURE 2, spinning ofthe mold is contintued until the pipe is at the proper temperature forpulling. Spinning of the mold is then stopped, and the core settingmechanism is withdrawn from the core in the formed pipe and moved awayfrom the end of the mold by extending the rod of cylinder 18. A new coreis immediately seated on the boss of the core setting mechanism, andpipe pulling apparatus 29 is moved into the end of the pipe in the mold.The pipe pulling mechanism has an expandable head that grips the insidesurface of the pipe and holds the pipe against movement as the travel ofcylinder 10 is reversed and the mold 5 is again moved over trough 8resulting in the extraction of the pipe from the mold.

When the Water box reaches a point where the pipe is free and the pipehas been rolled clear of the end of the mold, arm 27 swings into theposition shown in FIGURE 3 and spray coating is applied to the mold byspray nozzle 26. Arm 27 immediately swings clear of the mold, whilecylinder 18 is activated to move core 15' into position in the end ofthe mold. At this point the machine is ready to start through anothercasting cycle. I

It is important that the spray nozzle 23 be positioned to give completeand uniform coverage of the mold. If the nozzle is too far from the endof the trough, it does not adequately spray the mold in the area behindthe bell cavity, and-this area cannot be sprayed by a bell spray such asnozzle 26. The presence of the trough in the mold while nozzle 26 isspraying makes it impossible to spray any appreciable part of the moldbore by spraying from the bell end. On the other hand, if the nozzle 23is too close to the end of trough 8 it will spray into the metal whichis in the mold, onto the mold at a point which is too close to the areaof metal impingement to permit the moisture to dry out of the coatingslurry or down the barrel of the pipe being cast.

It is essential to direct the spray onto the mold so as to obtaincomplete coverage of a uniform coating having the desired wet spraycoating characteristics. An air atomized fan spray system such as iscommonly used for applying wet spray coatings to molds is satisfactory.Those skilled in the art will recognize that proper gun distance andslurry atomization must be maintained and space limitations make thisdifiicult in smaller size molds, however, methods have been devised toovercome this problem. When casting large pipe where there is adequatespace in the mold to accommodate the spray head in almost any position,the spray head can be mounted at an angle so as to give spray in whichthe fan is directed down at an angle of about 45 (see FIGURE 5).

In smaller pipe molds, there is little room for the spray nozzle and itis more difficult to obtain complete, uniform coverage of the mold. Forexample, in an eight inch mold the spray nozzle is not spaced far enoughfrom the mold surface to permit the nozzle to be pointed downward.However, it has been found that if the spray gun is mounted atapproximately 14" from the end of the pouring trough with its axis inthe horizontal plane parallel to the longitudinal axis of the mold andin the vertical plane at an angle of about 7 to the longitudinal axis ofthe mold (see FIGURE 4), a uniformcoating having the desiredcharacteristics can be obtained. This arrangement has also been found tobe satisfactory for casting 12" pipe.

In casting 6" and 8" pipe, desirable results have been obtained bymounting the spray gun with is axis parallel to the axis of the mold andproviding a large air hole in the air cap on the side next to the troughwhereby the spray fan is deflected away from the trough and onto themold (see FIGURE 6).

In practicing the present invention, the best results are obtained whenrapid casting rates are maintained with maximum delays. This results ina mold temperature that is hot enough to assure that the coating willdry almost instantly and that the metal solidification next to thecoating will be delayed sufficiently to permit the escape of gasesthrough the molten metaLWhenever a delay occurs at the end of a castingcycle, the mold should be retracted-from the trough and the coatingapplied even though metal is not being poured into the mold. When thisis done, the coating will dry satisfactorily and the mold will beproperly coated when casting is resumed.

I claim:

1. Method for making tubular metal castings by retractive casting in asubstantially horizontal mold comprising; positioning the mold andtrough so that the trough is within the mold, providing the end portionof the mold adjacent the spout of the trough with a wet spray coating,securing an end forming means in the end of the mold adjacent the spoutend of the trough, rotating the mold, appying a helical spiral of moltenmetal along the length of the mold and simultaneously spraying from anozzle positioned near the spout end of the trough a wet spray coatingonto the mold a short distance ahead of the leading edge of the helicalspiral of molten metal by providing relative longitudinal movementbetween the trough and mold, and extracting the pipe from the mold aftersolidification.

2. Method according to claim 1 wherein the molten metal and wet spraycoating are distributed along the mold by retracting the mold from thetrough.

3. Method according to claim 1 wherein the pipe is extracted from themold by securing the pipe in a stationary position and withdrawing themold from the pipe while simultaneously moving it over the trough.

4. Method according to claim 3 wherein the end of the mold adjacent thespout end of the trough is sprayed at the end of the extraction strokeof the mold.

References Cited UNITED STATES PATENTS I. SPENCER OVERHOLSER, PrimaryExaminer US. Cl. X.R.

